The current demand for water, water management and water treatment technologies is directly related to the increase in oil and gas demands in the emerging shale plays in the USA and international markets. In particular, oil shale plays and liquid rich plays will make up a significant portion of the energy mix in addition to water flood drives and other enhanced oil recovery (EOR) methods to extract from older fields. In most cases, improved, enhanced and unconventional methods, water is injected and therefore water and water management are key factors for energy production.
Unfortunately, in many parts of the USA and other markets where oil and gas operations are performed, water can be limited. The oil and gas industry is now considering ways to reduce fresh water consumption, and to recycle waste water as well as oil and gas produced or flow back waters.
Typically, waste water cannot be safely released into the environment or reused for other processes or applications until the main contaminates have been removed. There are a number of waste water sources from agriculture, mining—AMD (acid mine drainage), quarries, others and in particular, oil & gas industries, such as shale fracking operations. Waste from shale operations is of significant importance in these unconventional gas and oil plays.
Shale plays cannot be economically commercialized without being fractured, which usually involves large volumes of water and proppant to keep the fractures open after treatment. This significant water need often becomes problematic because of limited fresh and saline water availability, volume required, transportation cost and issues, containment and spill concerns, and increasing regulatory pressures. Each well can require up to 250,000 barrels, i.e., 10,500,000 gallons of water. During well testing, as much as 40% of the fluid pumped during the fracturing procedure is returned in the first 3-4 weeks of well testing. Often, water continues to be produced during the lifetime of the well. These waters are referred to as flowback and/or produced water. Contaminates in these fluids may include chlorides, surfactants, sulfates, boron, polymer, sand, silt, clays, heavy metals, oils, condensate, biocides, and/or other elements of environmental concern.
Current fluid disposal methods can be costly due to transportation and these fluids are often simply pumped into a salt water disposal well where they are permanently depleted from the ecological system. Current treatments of these fluids are often limited due to costs and efficiency. Treatment costs are usually directly associated with the amount of total dissolved solids in solution and many applications, such are reverse osmosis, are often limited due to the amount of solids in solution. Distillation to clean water is similarly limited by the amount of process water it produces before the water reaches saturation and salts precipitate. Other examples of fluid treatment on these waters have included, electrocoagulation, oxidation, chemical precipitation, macro or nano and ultra filtration, ion-exchange, forward osmosis, evaporation and even dilution with fresh water sources. Such treatments such as ion exchanges or chemical softening or precipitation often do not directly alter the TDS or total dissolved solids, do not degrade or remove VOC's, water soluble organics, PHC's and/or heavy metals of the solutions. Thus, new waste water treatment methods are needed which reduce the TDS (total dissolved solids), extract heavy metals, and degrading volatile organo-chlorides (VOC's), water soluble organics and petroleum hydro-carbons (PHC's) of a waste water solution.
Similarly, new water treatment methods are needed with respect to agricultural waste water. Such agricultural waste water commonly results from, for example, pig or hog farms, chicken farms, fish or shrimp farms, milk or dairy farms, and to a lesser extent cattle ranching. The contaminants of agricultural waste water differ depending upon the type of agriculture but may include, for example, high organic content, high solids, nitrogen compounds such as nitrates, phosphorus compounds, antibiotics, hormones, copper, etc. Such waste water is believed to contribute to a higher mortality rate for the animals and is also often accompanied by noxious odors. Accordingly, new treatment methods to reduce one or more the aforementioned contaminants and/or associated odors would be beneficial.
Likewise, hardrock mines such as gold, copper, uranium and the like generate significant amounts of waster water. Some estimates suggest there are from 17 to 27 billions of gallons of mining-related waste water in need of treatment. This waste water often comprises such contaminants as ammonias, cyanides, arsenic, cadmium, chromium, mercury, lead, nickel and the like. Moreover, treating mining-related waste water is often challenging
Advantageously, the present invention often meets all the aforementioned needs and more. In one embodiment the invention relates to a process for treating waste water. The process comprises contacting the waste water with an aqueous emulsion. The aqueous emulsion comprises one or more oil-liquid membranes surrounding a nano scale compound comprising iron, magnesium, or both. Typically, the weight ratio of emulsion to waste water is from about 1:150 to about 1:3000. The waste water and emulsion is then mixed for a time and under conditions sufficient to lower the surface tension of said waste water to between about 35 to about 75 dynes per cm at 25° C. according to the definition of kilogram-force for all gravitational units. This forms a substantially foam-like layer at the surface of the mixture. The foam-like layer is removed from the mixture such that the mixture comprises treated water.
In another embodiment, the present invention pertains to a process for treating waste water. The process comprises first removing at least a substantial portion of any floating oil and solids from the waste water to form pre-treated waste water. The pre-treated waste water is provided to a conduit connected to an open or closed vessel in a manner such that the pre-treated waste water moves through the conduit to the open vessel. An aqueous emulsion is injected into the conduit at one or more injection points wherein the aqueous emulsion comprises one or more oil-liquid membranes surrounding a nano scale compound of iron, magnesium, or both. The weight ratio of emulsion to pre-treated waste water is typically from about 1:150 to about 1:3000 and the residence time in the conduit is at least about 1 minute up to about 30 minutes. The conditions are such that the surface tension of said waste water is lowered to between about 35 to about 75 dynes per cm at 25° C. according to the definition of kilogram-force for all gravitational units prior to said pre-treated waste water entering said open vessel. An oxidizing agent is then contacted with the waste water in the open or closed vessel under conditions sufficient to form a substantially foam-like layer at the surface of the open or closed vessel and treated water below. The substantially foam-like layer at the surface of the open or closed vessel is then separated from the treated water.